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Various endogenous and environmental challenges of homoiostasis
have resulted in the evolution of apparently quite different
mechanisms for the same or similar functions in individual
representatives of the animal kingdom. One of the prominent
achievements of comparative physiology over the last few decades
has been the description of regula- tory features common to many
studied species beyond the extreme diversity of their morphological
forms. Delineation offunctional princi- ples universally applicable
to the physiology and biochemistry of living systems became often
possible through technical advances in the devel- opment of
numerous new techniques, in many cases modified and adopted from
other fields of science, but also by approaching certain problems
using multifactorial analysis. The advance in technology has
facilitated studies of minute functional details of mechanisms,
which finally lead to better understanding of generally similar
functions, covered by the multiple developments of Nature as a
response to an extreme variety of different conditions. Improved
understanding of specific mechanisms, however, has presented new
problems at the level of system integration. The importance of the
integrative aspect became particularly apparent during an
international symposium on 'Mecha- nisms of Systemic Regulation in
Lower Vertebrates: Respiration, Circu- lation, Ion Transfer and
Metabolism' (organized in 1990 by Norbert Heisler and Johannes
Piiper at the Max-Planck-Institut fUr experimen- telle Medizin at
Gottingen/Germany).
The originality of this volume is to reveal to the reader the
fascination of some unfamiliar sensory organs that are sometimes
ignored and often misunderstood. These receptors have only recently
been identified and their functional specificity is in some cases
still a matter for discussion. The four classes of sensory organs
considered here differ widely from one another in many respects.
One might even say that the only thing they have in common is that
they belong to cold-blooded vertebrates. These classes are: 1. the
directionally sensitive lateral-line mechanoreceptors of fishes and
amphi bians (Chapter 7); 2. the pseudobranchial organs of some
teleosts, equipped with pressoreceptors and at least three other
types of receptors (osmo- and chemoreceptors) (Chapter 8); 3. the
infrared-sensitive pit organs of some snake families (Chapter 9);
4. the various kinds of electroreceptors found in several marine
and freshwater fish families (Chapters 2 to 6). The first three
classes of receptors mentioned above thus rate only one chapter
each, whereas five chapters are devoted to the electroreceptors.
Electroreception has aroused enormous interest among physiologists
in specialties ranging from molecular biology to animal behavior.
The resulting quantity of research and discussion fully justifies
this disproportion. However, it cannot be denied that the contents
of the volume must appear unbalanced and heterogeneous, yet it
should not be perceived as a mere juxtaposition of particular and
unrelated cases."
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